The present invention relates to a speech synthesis method and apparatus based on a ruled synthesis scheme.
In general, in a ruled speech synthesis apparatus, synthesized speech is generated using one of a synthesis filter scheme (PARCOR, LSP, MLSA), a waveform edit scheme, and an impulse response waveform overlap-add scheme (Takayuki Nakajima & Torazo Suzuki, "Power Spectrum Envelope (PSE) Speech Analysis Synthesis System", Journal of Acoustic Society of Japan, Vol. 44, No. 11 (1988), pp. 824-832).
However, the above-mentioned schemes suffer the following shortcomings. The synthesis filter scheme requires a large volume of calculations, upon generating a speech waveform, and a delay in completing the calculations deteriorates the sound quality of synthesized speech. The waveform edit scheme requires a complicated waveform editing in correspondence with the pitch of synthesized speech, and hardly attains proper waveform editing, thus deteriorating the sound quality of synthesized speech. Furthermore, the impulse response waveform superposing scheme results in poor sound quality in waveform superposed portions.